[clang] [clang] Diagnose default arguments defined in different scopes (PR #124844)

[via cfe-commits]

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@@ -73,6 +73,11 @@ C++17 Feature Support
 Resolutions to C++ Defect Reports
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+- Clang now diagnoses ambiguous default arguments declared in different scopes
+  when calling functions, implementing [over.match.best] p4.
+  (`CWG1: What if two using-declarations refer to the same function but the declarations introduce different default-arguments? <https://cplusplus.github.io/CWG/issues/1.html>`_,
+  `CWG418: Imperfect wording on error on multiple default arguments on a called function <https://cplusplus.github.io/CWG/issues/418.html>`_)
+
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cor3ntin wrote:

As an aside should we augment our #GHXXXX logic to support #CWG123 and #LWG123? :D

https://github.com/llvm/llvm-project/pull/124844